Preheat oven to 400F (200C) and score skin
of each fish with 3-4 diagonal cuts. Rub inside and outside flesh of each fish with olive oil and drizzle
each fish with lemon juice. Sprinkle flesh evenly with salt and black pepper.
Place fish on a greased baking sheet. Meanwhile mix the rest of the ingredients
in a bowl (onion, spinach and rosemary sprigs) and place them inside each fish.

Roast for 30 minutes or until fish flakes
easily when tested with a fork. You may broil it for a couple of minutes for a
brownish top as well.